It is known to transmit multimedia signals, namely, video, voice, fax and data over unshielded twisted pair (UTP) conductor wiring in an asynchronous transfer mode. It is also known to configure UTP conductor in a multi-point topology.
In most modem offices, voice service is provided through a PABX (Private Automatic Branch Exchange), Key System, Centrex, or some combination of the above networks. Regardless of the equipment employed, communication to the desktop is provided over twisted pair wiring and the signal carried by this wiring is becoming increasingly digital in nature. However, the transmission rates used for digital transmission in this context rarely exceed 256 kb/s and although providing excellent voice quality, the technology represented by the PABX plus its distribution wiring is incapable of providing simultaneous data service at speeds greater than 128 kb/s. Accordingly, the traffic carried by the network is essentially at constant bit rate, i.e. isochronous in nature.
High speed data service is generally provided by some form of Local Area Network (LAN) wherein the wiring used for distribution may be coaxial cable or, in rarer cases, fibre optics. The data rates employed on these networks, typically, range from 10 Mb/s to 100 Mb/s. However, although the raw data rates provided by these networks far exceed that required for voice traffic, the networks are, in general, designed to support the "bursty" nature of data communications and are unable to guarantee the constant bit rate (CBR) service required for voice communications and other forms of isochronous traffic.
Video service, if it is available at all, requires both high bandwidth and CBR service and is often provided by a third separate distribution network, such as fibre optics. Some video networks take advantage of the fact that a structured wiring plan requires 4-pair distribution to each information outlet. If this information outlet is serviced by conventional 10BaseT ethernet, then only 2-pairs are required for said ethernet service, leaving a further 2-pairs unused. These unused pairs may be utilized by a video distribution system to create an entirely separate video network.
In summary, provision of each of the three services detailed above usually requires the installation of three separate networks in order to provide the grade of service required by each class of traffic at an economic cost that is acceptable. A number of newer technologies have been developed to meet the need for provision of multimedia services to the desktop. The most significant instances are:
isoEthernet: This technology permits 6 Mb/s of isochronous traffic to be transmitted concurrently with 10 Mb/s of conventional Ethernet traffic. However, the aggregate capacity of 16 Mb/s is modest by modern standards and its ability to adapt to varying mixes of isochronous and asynchronous traffic is limited. Provisioning of larger networks is complex since the demands of each type of traffic may dictate differing (or even incompatible) network topologies. PA1 100VG-AnyLAN: This technology allows for 100 Mb/s traffic capacity over 4-pairs of UTP-3. Although it does permit any mixture of traffic types to be carried, scaleability is limited by the network delay and synchronization requirements. PA1 ATM-25, ATM-155: These transmission systems are based on Asynchronous Transfer Mode technology and provide complete flexibility to build both local and wide area networks and possess sufficient bandwidth to support all known applications. The approaches taken by the aforementioned technologies are summarized in the following table: PA1 a) feeding input digital signals selected from the group consisting of voice, fax, video and data from the signal nodes; PA1 b) controlling allocation of bandwidth to the input digital signals as between the sending stations; PA1 c) providing a source data stream in binary format derived from the allocated input digital signals; PA1 d) converting the source data stream into a digital symbol stream capable of being transmitted over the wiring; PA1 e) driving and filtering the digital symbol stream over the wiring; PA1 f) splitting the filtered digital symbol stream into a plurality of replicated digital symbol streams; PA1 g) amplifying and selecting each of the plurality of replicated digital symbol streams to provide an amplified and selected digital symbol stream; PA1 h) converting the amplified and selected digital symbol stream into a sink data stream in binary format; PA1 i) identifying and selecting desired digital signals of the sink data stream for the plurality of the receiving stations; and PA1 j) delivering the identified and selected digital signals to the signal nodes. PA1 feeding a first input digital signal at a selected first voltage and power to an amplifier; PA1 amplifying the first input digital signal to a second voltage and power; PA1 splitting the amplified digital signal to provide the plurality of replicated digital symbol streams at a third voltage and power; and PA1 feeding each of the replicated digital symbol streams to an output line. PA1 a) feeding the input digital signal at the selected voltage and power to the primary coil of a transformer; PA1 b) providing the transformer with a secondary coil possessing a centre-tap; PA1 c) feeding the signal derived from each half of the secondary coil to an output transformer; and PA1 d) feeding an output digital signal derived from each of the output transformers to an output line. PA1 a) feeding the output digital signal at a selected second voltage and power to the primary coil of a second transformer having a secondary coil possessing a centre-tap; PA1 b) feeding the signal derived from each half of the secondary coil to an output transformer; and PA1 c) feeding an output digital signal derived from each of the output transformers to an output line. PA1 a) synchronizing the symbol stream to a clock source; PA1 b) encoding the data stream according to a pre-selected algorithm; and PA1 c) looping back the symbol stream for diagnostic purposes. PA1 detecting presence of activity in the symbol stream; PA1 generating a clock rate from the symbol stream; PA1 aligning sampling frequency and phase with the symbol stream; and PA1 decoding the symbol stream into a binary format according to a predefined algorithm. PA1 synchronizing the symbol stream to a clock source; PA1 encoding the data stream according to a pre-selected algorithm; PA1 looping back the symbol stream for diagnostic purposes; PA1 detecting presence of activity in the symbol stream; PA1 recovering and regenerating a clock rate from the symbol stream; PA1 aligning sampling frequency and phase with the symbol stream; and PA1 decoding the symbol stream into a binary format according to a pre-defined algorithm. PA1 a) amplifying and selecting the filtered digital symbol stream to provide an amplified digital symbol stream; PA1 b) regenerating the amplified digital symbol stream to provide a regenerated digital symbol stream; PA1 c) splitting the regenerated symbol stream into a plurality of replicated digital symbol streams; and PA1 d) driving and filtering the replicated digital symbol stream over the wiring. PA1 recovering a clock signal from the digital symbol stream; PA1 sampling the data stream to acquire the original data content; and PA1 generating a digital symbol stream from the original data content; and may further comprise regenerating a plurality of digital symbol streams from a plurality of sending stations. PA1 a) circuitry constructed and adapted to feed input signals selected from the group consisting of voice, fax, video and data from the sending stations along the wiring; PA1 b) circuitry constructed and adapted to control allocation of bandwidth to the digital signals as between the sending stations; PA1 c) circuitry constructed and adapted to provide a source data stream in binary format derived from the allocated input digital signals; PA1 d) circuitry constructed and adapted to convert the source data stream into a digital symbol stream capable of being transmitted over the wiring; PA1 e) circuitry constructed and adapted to drive and filter the digital symbol stream over the wiring; PA1 f) circuitry constructed and adapted to split the filtered digital symbol stream into a plurality of replicated digital symbol streams; PA1 g) circuitry constructed and adapted to amplify and select each of the plurality of replicated digital symbol streams to provide an amplified and selected digital symbol stream; PA1 h) circuitry constructed and adapted to convert the amplified and selected digital symbol stream into a sink data stream in binary format; PA1 i) circuitry constructed and adapted to identify and select desired digital signals of the sink data stream for the plurality of the receiving stations; and PA1 j) circuitry constructed and adapted to deliver the identified and selected digital signals to the signal nodes. PA1 circuitry constructed and adapted to feed a first digital input signal at a selected first voltage and power to an amplifier; PA1 circuitry constructed and adapted to amplify the first input digital signal to a second voltage; PA1 circuitry constructed and adapted to split the amplified digital signal to provide the plurality of split output replicated digital signal streams at a third voltage and power; and PA1 circuitry constructed and adapted to feed each of the replicated digital symbol streams to an output line. PA1 circuitry constructed and adapted to feed the input digital signal at the selected first voltage and power to the primary coil of a transformer; PA1 circuitry constructed and adapted to provide the transformer with a secondary coil possessing a centre-tap; PA1 circuitry constructed and adapted to feed the signal derived from each half of the secondary coil to an output transformer; and PA1 circuitry constructed and adapted to feed an output digital signal derived from each of the output transformers to an output line. PA1 circuitry constructed and adapted to feed the output digital signal at a selected second voltage and power to the primary coil of a second transformer having a secondary coil possessing a centre-tap; PA1 circuitry constructed and adapted to feed the signal derived from each half of the secondary coil to an output transformer; and PA1 circuitry constructed and adapted to feed an output digital signal derived from each of the output transformers to an output line. PA1 circuitry constructed and adapted to synchronize symbol stream to clock source; PA1 circuitry constructed and adapted to encode the data stream according to a pre-selected algorithm; and PA1 circuitry constructed and adapted to loop back the symbol stream for diagnostic purposes. PA1 circuitry constructed and adapted to detect presence of activity in the symbol stream; PA1 circuitry constructed and adapted to generate a clock rate from the symbol stream; PA1 circuitry constructed and adapted to align sampling frequency and phase with the symbol stream; and PA1 circuitry constructed and adapted to decode the symbol stream into a binary format according to a pre-defined algorithm. PA1 circuitry constructed and adapted to synchronize the symbol stream to clock source; PA1 circuitry constructed and adapted to encode the data stream according to a pre-selected algorithm; PA1 circuitry constructed and adapted to loop back the symbol stream for diagnostic purposes; PA1 circuitry constructed and adapted to detect presence of activity in the symbol stream; PA1 circuitry constructed and adapted to generate a clock rate from the symbol stream; PA1 circuitry constructed and adapted to align sampling frequency and phase with the symbol stream; and PA1 circuitry constructed and adapted to decode the symbol stream into a binary format according to a pre-defined algorithm. PA1 (i) circuitry constructed and adapted to amplify and select the plurality of replicated digital symbol streams to provide a first amplified and selected digital symbol stream; PA1 (ii) circuitry constructed and adapted to regenerate one of the first amplified and selected digital symbol streams to provide an enhanced replicated digital symbol stream to extend transmission wiring distance; PA1 (iii) circuitry constructed and adapted to split the enhanced replicated digital symbol stream into a plurality of replicated enhanced replicated digital symbol streams; PA1 (iv) circuitry constructed and adapted to drive and filter the enhanced replicated digital symbol stream over the wiring. PA1 circuitry constructed and adapted to recover a clock signal from the digital symbol stream; PA1 circuitry constructed and adapted to sample the data stream to acquire the original data content; and PA1 circuitry constructed and adapted to generate a digital symbol stream from the original data content. PA1 synchronizing the symbol stream to clock source; PA1 encoding the data stream according to a pre-selected algorithm; and PA1 looping back the symbol stream for diagnostic purposes. PA1 detecting presence of activity in the symbol stream; PA1 generating a clock rate from the symbol stream; PA1 aligning sampling frequency and phase with the symbol stream; and PA1 decoding the symbol stream into a binary format according to a predefined algorithm. PA1 circuitry constructed and adapted to synchronize the symbol stream to clock source; PA1 circuitry constructed and adapted to encode the data stream according to a pre-selected algorithm; and PA1 circuitry constructed and adapted to loop back the symbol stream for diagnostic purposes. PA1 circuitry constructed and adapted to detect the presence of activity in the symbol stream; PA1 circuitry constructed and adapted to generate a clock rate from the symbol stream; PA1 circuitry constructed and adapted to align sampling frequency and phase with the symbol stream; and PA1 circuitry constructed and adapted to decode the symbol stream into a binary format according to a pre-defined algorithm. PA1 feeding a first digital input signal at a selected first voltage and power to an amplifier; PA1 amplifying the first input digital signal to a second voltage; and PA1 splitting the amplified digital signal to provide the plurality of split output replicated digital signal streams at a third voltage and power. PA1 separating AC and DC signals present at a port and protecting from excessive or reversed voltages; PA1 generating a regulated DC supply voltage from the DC signal; PA1 amplifying the AC signal using positive feedback in a single port amplifier; PA1 distributing the amplified AC signal to a plurality of input/output ports; PA1 matching the impedance of the input/output ports to that of the attached twisted pair wiring; and PA1 maintaining correct termination of each port when stations are disconnected from the twisted pair wiring. PA1 circuitry constructed and adapted to feed a first digital input signal at a selected first voltage and power to an amplifier; PA1 circuitry constructed and adapted to amplify the first input digital signal to a second voltage; and PA1 circuitry constructed and adapted to split the amplified digital signal to provide the plurality of split output replicated digital signal streams at a third voltage and power. PA1 recovering a clock signal from the digital symbol stream; PA1 sampling the data stream to acquire the original data content; an PA1 generating a digital symbol stream from the original data content. PA1 recovering a clock signal from the digital symbol stream; PA1 sampling the digital symbol stream to acquire the original data content; and PA1 generating a regenerated digital symbol stream from said original data content. PA1 circuitry constructed and adapted to recover a clock signal from a digital symbol stream; PA1 circuitry constructed and adapted to sample the data stream to acquire the original data content; and PA1 circuitry constructed and adapted to generate a digital symbol stream from the original data content. PA1 providing power amplification of the digital symbol stream; PA1 limiting the bandwidth of the transmitted signal; and PA1 selecting the number of wire-pairs used for transmission. PA1 providing correct termination of the transmission system; PA1 amplifying the digital symbol stream with equalization of frequency-dependent attenuation; PA1 detecting the amplified digital symbol stream in the presence of noise; and PA1 regenerating a clock frequency from the amplified digital symbol stream..
TABLE 1 __________________________________________________________________________ Local Area Network Technologies Topology Media Access Method Isochro- Packet Length Point - Multi- CSMA/ nous Fixed Var'ble Point point Token CD TDMA __________________________________________________________________________ Ethernet .check mark. .check mark. .check mark. Fast Ethernet .check mark. .check mark. .check mark. Token Ring .check mark. .check mark. .check mark. iso-Ethernet .check mark. .check mark. .check mark. .check mark. .check mark. 100VG- .check mark. .check mark. .check mark. .check mark. AnyLAN ATM-25/155 .check mark. .check mark. .check mark. -- -- -- The .check mark. .check mark. .check mark. .check mark. Invention __________________________________________________________________________
The preceeding table indicates that Ethernet, Fast Ethernet and Token Ring technologies do not provide a capability to transmit isochronous information and are therefore unsuitable for the purpose intended herein. iso-Ethernet provides multi-media service by segregating isochronous and asynchronous traffic, using separate media access methods (Time Division Multiple Access--TDMA; and Carrier Sense Multiple Access with Collision Detection--CSMA/CD) for each traffic type.
100VG-AnyLAN utilizes a token-based system for guaranteeing response time to isochronous traffic, but is not compatible with the ATM Adaptation Layer formats required for national level internetworking. It also requires 4-pair wiring distribution. The various ATM physical layer distribution systems do not provide a multipoint mechanism for the construction of cost-effective Local Area Networks.
In addition to the aforementioned limitations, none of the above technologies provides a cost-effective solution for low data-rate and low-value applications, such as basic telephony. In particular, there are no known systems which are able to support all of the above services concurrently over shared twisted pair wiring at a cost that is comparable to that of state-of-the-art-voice-only systems.
However, there is a need for apparatus and methods which provide all of the aforesaid transmission features in an improved cost effective manner.